Electrostatic induction conversion device

Abstract

There is provided an electrostatic induction conversion device which is small, has high conversion efficiency between electric energy and kinetic energy, and can prevent degradation of an electret. The electret is formed by injecting an electric charge into the vicinity of the surface of an insulating material, is disposed between two conductors, and is constructed so that it moves relatively to at least one of the conductors opposite to the electret and converts between electric energy and kinetic energy. As the insulating material forming the electret, it is preferable to use a polymer having a fluorine-containing aliphatic cyclic structure.

1. An electrostatic induction conversion device for converting between electric energy and kinetic energy, comprising:
 an electret moving relatively to a conductor; and 
 a moisture-proof film covering the electret, wherein the moisture-proof film is made of polyparaxylylene or a derivative of polyparaxylylene. 
 
     
     
       2. An electrostatic induction conversion device according to  claim 1 , wherein the electret is made of PTFE (polytetrafluoroethylene), FEP (fluorinated ethylene propylene copolymer), PFA (tetra fluoro ethylene-perfluoro alkylvinyl ether copolymer), silicon oxide or a polymer having a fluorine-containing aliphatic cyclic structure. 
     
     
       3. An electrostatic induction conversion device according to  claim 1 , wherein the electret is made of a polymer which is obtained by cyclopolymerizing a fluorine-containing monomer having two or more polymerizable double bonds and has a fluorine-containing aliphatic cyclic structure in a main chain. 
     
     
       4. An electrostatic induction conversion device according to  claim 3 , wherein the fluorine-containing aliphatic cyclic structure includes one or less etheric oxygen atom. 
     
     
       5. An electrostatic induction conversion device according to  claim 3 , wherein the electret made of the polymer has a thickness of 10 μm or more, and a surface charge density of 1 mC/m 2  or more.